|Function-based screening||Sequence-based screening||SIGEX|
|Screening principle||• Detecting changes by enzymatic reactions (e.g. halo formation around the colonies)||• PCR or Southern hybridization based on the DNA sequence consensus||• Trapping the operon induced by a substrate and sorting using FACS|
• Secures a complete form of gene or gene cluster required for desired traits|
• Potentially obtains completely novel genes.
|• Overcomes the limitations of the heterologous expression||
• Fast and economical|
• Any substrates that can be introduced into cytoplasm can be used in its native forms.
|Disadvantages||• Must satisfy the expression conditions (transcription, translation, folding, secretion) in heterologous hosts||
• Requires a database and analyses of the DNA sequence consensus.|
• Does not guarantee the acquisition of complete forms of genes or gene clusters.
• Sensitive to the orientation of the genes with desired traits|
• Cannot use substrates that do not migrate to cytoplasm
• Sensitive to the initial FACS setting
|Examples||antibiotics [9, 19-22], genes involved antibiotic resistance [9, 23, 24], agarases , amidases , amylases [15, 21, 25, 26], esterase/lipases [8, 15, 21, 27, 28], xylanases , 4-hydoxybutyrate dehydrogenase  alcohol oxidoreductases , pectate lyases ||amylases , polyketide synthases [32, 33]||Benzoate-degratative or catechol degradative operon, P450 enzyme |